Unalterable ohmic resistance



$615.4, w3@ s, EWE 3,745,939

UNALTERABLE OHMIC RESISTANCE Filed April 29. 1927 INVENTOR SIEGMUND LOEWE TORNEY Patented Feb. 4, 1930 AMERICA, A

NAU, GERMANY, ASSIGNOR TO RADIO CORPORATION F DELAWARE UNALTERAJBLE OHMIC RESISTANCE .Application and apra 29,192?, serial no.

This invention relates to a high ohmic resistance and especially to a method for making a resistance of the coated rod type for use in multiple unit tubes. E; Multiple-unit tubes contain' a amplifier systems together with the corresponding coupling means inside one and the same vacuous space, said coupling means consisting usually of what is @own as the cain pacfity-resistance arrangement. When such high-ohmic resistances are to be built into the vacuous space of a multiple-unity tube, they must be insensitive to temperature iniiuences.

During the manufacture of high-vacuum it tubes, it is necessary to apply some prolonged heating to a oint in the degrees, for t e purposes of removing the last traces of water vapors. During this thermal treatment, the resistance value of built in a@ high-ohmic resistances shouldnot'be permanently altered, indeed, after completion oit the exhaustV and after cooling of the-tube, the resistance must be restored to its previous value. Y A Now tests have sho sistances which are ,suited orheing built into multiple-unit tubes can he made in a manner to be hereinafter described. Generally these resistances aremown4 as the so-called vacuum resistances which consist of an insulation support or carrier and which are coated with a i'eebly conducting layer, and are separately enclosed in a vacuous space.

Such a resistance is shown, for example, in the accompanying drawing.

The numeral l represents the rod carrier, 2 a deposit thereon and 3 the leads leading thereto.

As a general rule, these resistances are not insensitlve to theaction of heat up to 400 degrecs, but, in case of prolonged heating at these temperatures, they change'quite considerably in their resistance value. Vacuum resistances of this kind are made by squirting upon or spraying upon the insulating carrier l, which is usually; made of glass and which at its ends is urnished with sealed supply electrodes 3, a layer in heat, said layer consisting of colloidal carbon including an addition 4ranging between 3 and 10% of a binder plurality of neighborhood of 400 l wn that high-ohmic reb 187,677, and inserm-.ny :my 1e, ieee;

). ik'lhe latter usually conc, linseedZ grape sugar, or

(protective colloid sists of gumarabi dextrin.

'lests vhave shown th ances which are multiple-unit tu athigh-ohmic resistsuitable for 'being built into bes, may be made by means of the same manufacturing method, if during the manufacture of the resistance, it is heated for some prolonged period of time at a somewhat higher temperature than the one prevailing during the process of exhausting the bulb or tube. Resistances of this kind insensitive to temperature influences are obtained, for example, by spraying a colloid solution containing from 3 to 10% of a protective coloid, upon the resistance carrier Aor support, whereupon the resistance after having been placed in a small vacuous space, is heated for l5 to 30'minutes at, say, 420 degrees C. During such heating in vacuo, the protective colloid is converted into elementary carbon, with an incidental, almost complete, extraction of Water. The connecting resistance Elm then consists'almost completely of elementary caron. l 75 Tests have shown that resistance so made can be heated any number of times and for any desired periods to lower temperatures, say, around 400 degrees C. without any apprecable alteration in resistance value being occasioned.

ll claim as my invention: i

l. The method of making a resistance unit for evacuated tubes which includes first coating an insulating carrier with a colloidal solution containing carbon and not more than l0 per cent of a protective binder, and then heating said coated carrier in vacuo to a high temperature.

2. The method of resistance which incl loidal 4solution inclu tective binder, heating said b making a high-ohmic udes rst applying a colding carbon and a proto an insulating body, and then ody in vacuo up to 420 degrees C., until a coating of substantially elementary carbon free of occluded gases is formed on said body 3. The method of making a high-ohmic restance suitable for "use in a multiple-unit tube which consists in coating an insulating coA carrier with a solutlon containing colloidalcarbon and 3 to 10 per cent of a protective colloid, and then subjecting said coated carrier in vacuo to a temperature in the region of 420 C.

-SIEGMUND LOEWE. 

